Abstract
Toxoplasma gondii is a ubiquitous protozoan parasite that can infect all warm-blooded animals, including both mammals and birds. Protein disulfide isomerase (PDI) localises to the surface of T. gondii tachyzoites and modulates the interactions between parasite and host cells. In this study, the protective efficacy of recombinant T. gondii PDI (rTgPDI) as a vaccine candidate against T. gondii infection in BALB/c mice was evaluated. rTgPDI was expressed and purified from Escherichia coli. Five groups of animals (10 animals/group) were immunised with 10, 20, 30, 40 μg of rTgPDI per mouse or with PBS as a control group. All immunisations were performed via the nasal route at 1, 14 and 21 days. Two weeks after the last immunisation, the immune responses were evaluated by lymphoproliferative assays and by cytokine and antibody measurements. The immunised mice were challenged with tachyzoites of the virulent T. gondii RH strain on the 14th day after the last immunisation. Following the challenge, the tachyzoite loads in tissues were assessed, and animal survival time was recorded. Our results showed that the group immunised with 30 μg rTgPDI showed significantly higher levels of specific antibodies against the recombinant protein, a strong lymphoproliferative response and significantly higher levels of IgG2a, IFN-gamma (IFN-γ), IL-2 and IL-4 production compared with other doses and control groups. While no changes in IL-10 levels were detected. After being challenged with T. gondii tachyzoites, the numbers of tachyzoites in brain and liver tissues from the rTgPDI group were significantly reduced compared with those of the control group, and the survival time of the mice in the rTgPDI group was longer than that of mice in the control group. Our results showed that immunisation with rTgPDI elicited a protective immune reaction and suggested that rTgPDI might represent a promising vaccine candidate for combating toxoplasmosis.
Highlights
Toxoplasma gondii is a ubiquitous protozoan parasite that can infect virtually all warm-blooded animals, including both mammals and birds
After induction with 0.1 mM IPTG at 25uC, the recombinant T. gondii PDI (rTgPDI) proteins were successfully expressed in E. coli and the molecular weight was approximately 57 KDa (Fig. 2A)
Western blotting analysis indicated that the rTgPDI band was able to react with the rabbit anti-T. gondii serum polyclonal antibody and anti-His antibody (Fig. 2C)
Summary
Toxoplasma gondii is a ubiquitous protozoan parasite that can infect virtually all warm-blooded animals, including both mammals and birds. Only an attenuated vaccine (Toxovax, Intervet Shering-Plough) based on the live attenuated S48 strain has been licensed for use in sheep in Europe and New Zealand for over two decades [9] The drawbacks of this vaccine are short shelf-life, adverse effects, and the potential risk of reverting to a pathogenic strain. Some evidences have suggested that PDIs are present at cell surface They functionality modulate cellular interactions with a number of pathogens [21]. The antibody might be upregulated as a continuous mucosal defence against protozoan parasites [25] These observations strongly suggest that TgPDI could serve as a candidate vaccine antigen. After the challenge with tachyzoites from the RH strain of T. gondii, the numbers of brain and liver tachyzoites in the BALB/c mice were recorded, and the survival time of rTgPDI-immunised mice was observed
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
